Reverberatory screen for a radiant burner

Abstract

The present invention relates to porous mat gas fired radiant burner panels utilizing improved reverberatory screens. The purpose of these screens is to boost the overall radiant output of the burner relative to a burner using no screen and the same fuel-air flow rates. In one embodiment, the reverberatory screen is fabricated from ceramic composite material, which can withstand higher operating temperatures than its metallic equivalent. In another embodiment the reverberatory screen is corrugated. The corrugations add stiffness which helps to resist creep and thermally induced distortions due to temperature or thermal expansion coefficient differences. As an added benefit, it has been unexpectedly discovered that the corrugations further increase the radiant efficiency of the burner. In a preferred embodiment, the reverberatory screen is both corrugated and made from ceramic composite material.

What is claimed is: 
     
       1. A reverberatory screen for a radiant burner, comprising: a plurality of ligaments woven together to form an open mesh structure, wherein a ligament comprises at least one ceramic fiber, further wherein a junction or intersection of two or more ligaments defines at least a portion of an opening of said open mesh structure;   a corrugation imposed on said open mesh structure in more than one direction;   a ceramic matrix embedding at least one ligament; and   at least one debond material disposed between said ligament and said matrix to permit pull-out of said at least one fiber relative to said matrix upon application of fracture stress to said matrix.   
     
     
       2. The reverberatory screen of claim 1, further comprising providing at least one oxygen scavenger material to the ceramic matrix composite material, the oxygen scavenger material contacting at least one of the fiber, the matrix or the debond material. 
     
     
       3. The reverberatory screen of claim 2, wherein said oxygen scavenger material comprises at least material selected from the group consisting of boron carbide and boron nitride. 
     
     
       4. The reverberatory screen of claim 1, wherein the matrix comprises at least one material selected from the group consisting of silicon carbide, silicon nitride and aluminum oxide. 
     
     
       5. The reverberatory screen of claim 1, wherein said at least one ceramic fiber is selected from the group consisting of silicon carbide, aluminum oxide and aluminosilicates. 
     
     
       6. The reverberatory screen of claim 1, where said debond material comprises a material selected from the group consisting of pyrolytic carbon, resin char carbon, and boron nitride. 
     
     
       7. The reverberatory screen of claim 1, wherein at least one ligament comprises a fiber tow. 
     
     
       8. The reverberatory screen of 1, further comprising reinforcement along an edge of said screen in at least one direction of said corrugation. 
     
     
       9. The corrugated grid of claim 1, wherein a total of said openings comprises from about 30 percent to about 70 percent of the total area bounded by a perimeter of said grid. 
     
     
       10. The reverberatory screen of claim 1, wherein each ceramic fiber comprises a continuous fiber embedded in said ceramic matrix. 
     
     
       11. The reverberatory screen of claim 10, wherein at least a portion of said continuous fibers are provided in the form of a tow, and further comprising at least two sets of fiber tows, each of said tows within each set being substantially parallel to one another. 
     
     
       12. The reverberatory screen of claim 11, wherein said fiber tows of one set contact said fiber tows of another set to form a screen of regularly spaced ligaments and openings therebetween. 
     
     
       13. The reverberatory screen of claim 12, wherein said contacting fiber tows are woven. 
     
     
       14. The reverberatory screen of claim 11, wherein said continuous fibers are about 10 to 25 microns in diameter. 
     
     
       15. The reverberatory screen of claim 11, wherein at least one of said fiber tows comprises more than about 50 fibers. 
     
     
       16. The reverberatory screen of claim 11, wherein said fibers and said ceramic matrix comprise silicon carbide, and said at least one debond material comprises carbon. 
     
     
       17. The reverberatory screen of claim 11, further comprising an oxidation protection material disposed between said fibers and said matrix.